Probiotics get it in the gut

Yogurt is one of the foods to which probiotics are being added in an attempt to increase health benefits. (Shutterstock.com)

Think bacteria, and what comes to mind is something bad: Infection, disease, even death. After all, bacteria are responsible for everything from garbage decay to strep throat, from gum disease to bubonic plague.

But when it comes to your body, the world of bacteria is actually made up of good guys and bad. Not only are most bacteria completely harmless, many are actually good for you. The trouble is, those good bacteria are being muscled out by hard living, stress and antibiotics - so much so that a thriving industry is aimed at putting them back.

That's the explanation behind the success of probiotics, the so-called "good" bacteria that are now sold as supplements or added to foods such as yogurt. (The global probiotics marketed generated $15.9 billion in 2008.)

Your gut, which is home to billions of bacteria, needs a proper balance of different kinds of bacteria to stay healthy. Probiotics (the term means pro-life) are believed to put back the beneficial bacteria in your gut that may be depleted through stress, an unbalanced diet, alcohol consumption or antibiotics and other medications.

At a recent seminar hosted by the Canadian Institutes of Health Research, the University of Alberta's Dr. Karen Madsen defined probiotics as "monocultures or mixed cultures of live non-pathogenic micro-organisms that benefit the health of the host. Harnessing of bacteria for our benefit is not new," she said. In 1877, Louis Pasteur noticed that "common bacilli" could suppress anthrax growth. It was another scientist, Elie Metchnikoff, who in 1907 isolated bacteria made from fermented milk and observed that the Balkan people of Eastern Europe who drank it lived longer.

"We used to eat lots of fermented foods, but we don't now," Dr. Madsen told her audience. "Today we have refrigeration and refined foods." Probiotics, she added, is putting back into foods (or in pill form) the beneficial bacteria that used to be in food.

It is only recently, however, that probiotics have earned a higher profile in gastroenterological research. Studies on patients with inflammatory bowel diseases such as Crohn's and ulcerative colitis show that probiotics affect mucosal surfaces including the mouth and the gastrointestinal tract.

Scientists are now able to explain how, in a healthy colon and intestines, friendly bacteria compete with unfriendly types. Probiotics, it seems, interact at various levels of the gut; they pass signals back and forth between themselves, the epithelial cells that line the intestine and the cells in the immune system. The result can be the strengthening of the immune system.

Dr. Madsen said that probiotics alter irritable bowel syndrome "possibly through their anti-inflammatory actions, their ability to reduce visceral hypersensitivity, and their ability to modulate the gut microflora."

Apparently, they're also an inexpensive way to prevent the spread of disease: In one study, nursing home patients were given probiotics in a yogurt drink to help prevent the spread of C-difficile. Probiotics can help prevent diarrhea, particularly the result of treatment with antibiotics; they can also prevent yeast infections, reduce lactose intolerance, promote regularity, and protect against bladder cancer.

But critics of probiotics say that research is still needed because the benefits of probiotics seem to be strain-dependent: Since each person's gut's flora is different, it's hard to know which strains you need to balance your particular microflora. A lot more needs to be done to help consumers sort fact from fiction, too: A few years ago, one yogurt company was sued for pumping up its probiotic health claims; probiotics' exaggerated Internet claims further confuse and frustrate consumers who want to take charge of their health.

"All probiotics are not alike," warned Dr. Madsen, explaining that depending on the strain, a probiotic can do anything from strengthening the immune system to decreasing inflammation. "Prevention rather than treatment is where probiotics shine."

What's in probiotics?

Most probiotic products contain bacteria isolated from milk products, typically Lactobacillis and Bifidobacterium. Other lactic acid bacteria include L-bulgaricus and L-acidophilus. Health Canada's guidelines say that food companies should name each probiotic culture used and limit their claims to those that refer to maintaining body functions. (Check out www.hc-sc.gc.ca.)

Dig deeper

Probiotics may not even help you; some have done harm. Ask yourself if there's any evidence that a probiotics product actually confers a health benefit. Try to determine how much is needed to see this benefit. Always seek further scientific evidence from the company's website.

How they work

According to Reader's Digest's Foods That Harm, Foods That Heal, probiotics have a number of modes of activity, "including affecting inflammatory processes, secreting compounds that regulate cell function, and protecting the intestine against invasive bad bacteria. They inhibit the growth of disease-causing bacteria by preventing their attachment to the intestine and by producing substances that suppress their growth."